Converting device



3 Sheets-ShamI l Filed July 15, 1953 IIII/ Feb. 4, 1958 H. BHM ET AL CONVERTING DEVICE Filed July l5, 1953 5 Sheets-Sheet 2 U V W [nz/enter.'

Feb. 4, 1958 H. BHM ET Al.

coNvERTING DEVICE 5 Sheets-Sheet 3 Filed July 15, 1955 Inventor'.

m c KM United States Patent 0 CONVERTING DEVICE Hellmuth Bhm and Paul Kuhnert, Berlin-Charlottenburg,

Germany, assignors to Licentia Patent-Verwaltungs- G. m. b. H., Hamburg, Germany Application July 15, 1953, Serial No. 368,194 Claims priority, application Germany October 8, 1951 18 Claims. (Cl. 321-48) The present invention relates to a converting device which can be used as a rectifier, inverter or transverter.

This application is a continuation in part of our previously tiled U. S. application Serial Number 313,422 and entitled Converting Device, now abandoned.

Such converting devices have become known in which a liquid jet rotates in a vessel containing a vacuum or a protecting gas and is sprayed against stationary contacts in order to make a Contact. In these devices the driving motor is enclosed by the vessel. Furthermore it is known in connection herewith to effect the interruption of the current only within the liquid jet.

It is an object of the present invention to reduce the Contact resistance of the converting device.

According to the present invention the contacts or electrodes are formed so that the liquid jet, particularly a jet of mercury, is attened or squeezed between the electro-des arranged at a small distance apart so that the contact resistance is considerably reduced. On the other hand the arrangement should be made in such a manner that the curtain of mercury formed thereby is projected outward by centrifugal force into the gaps between the stationary electrodes, that is, during the commutation, and does not cause irregular short circuits.

A converting device according to the invention comprises in its broadest aspect a plurality of stationary contacts arranged along a circle and separated from one another by gaps, means for directing a rotating electroconductive jet against the stationary contacts one after the other, the jet forming a Contact resistance with the stationary contacts, and means cooperating with the stationary contacts for imparting a curtain-like shape to the jet so as to decrease the contact resistance, the curtain- Shaped jet being forced by centrifugal force into the gaps between the stationary contacts.

Preferably the device includes a hollow rotating contact and means for forcing an electro-conductive liquid through the rotating contact, the liquid forming a jet being squeezed into curtain-like shape when the rotating contact passes along any of the stationary contacts.

A preferred embodiment of the present invention comprises in combination a closed vessel, a plurality of stationary contacts arranged in the closed vessel along a circle and separated from one another by gaps, the stationary contacts having stationary contact faces, a hollow body arranged for rotation in the closed vessel, the hollow body having a rotating Contact face rotating on a circle concentric with, and having a diameter being slightly smaller than the diameter of, the circle along which the stationary contacts are arranged, the hollow body having an opening arranged at the lower end thereof and a nozzle opening in the rotating contact face, and a pool of mercury arranged in the closed vessel so as to cover the opening arranged at the lower end of the hollow body, whereby by the rotation of the hollow body mercury is sucked in through the opening and forced out of the hollow body through the nozzle as a jet which is squeezed into curtainlike shape when the rotating contact face passes along ice any of the stationary contacts, the curtain-like jet being forced by centrifugal force into the gaps between the stationary contacts and being thrown against the walls of the vessel where the jet is broken up into droplets collecting in the pool of mercury.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a sectional elevation of an embodiment of the present invention;

Fig. la is a wiring diagram of the embodiment of Fig. l;

Fig. 2 is a plan view of the device shown in Fig. l seen from below;

Fig. 3 shows a modification of Fig. l;

Fig. 4 is a sectional elevation of another embodiment of the present invention;

Fig. 5 shows another modification of the devices shown in Figs. 1 4;

Fig. 6 is a wiring diagram of a control circuit for a three phase motor according to the invention;

Fig. 7 is another wiring diagram according to the present invention;

Fig. 8 is an embodiment similaito Fig. 5 of the present invention;

Fig. 8a is a partial plan view taken through Srl-8a of Fig. 8;

Figs. 9, l() and ll are diagrams for the explanation of the present invention;

Fig. l2 shows a further embodiment of the present in vention together with the wiring diagram of the parts connected thereto;

Fig. 13 illustrates an arrangement for adjusting the phase of a rotating centrifuge; and

Fig. 14 illustrates another embodiment for adjusting the phase of a rotating centrifuge.

Referring now to the drawings and first to Figs. l, la and 2, a shaft 1 driven by a motor 135 carries a mercury centrifuge 2 which rotates in direction of the arrow A shown in Fig. 2. The centrifuge 2 comprises two pipes 3 and 4 which communicate at the lower ends thereof with an opening 5a submerged in a liquid 5 Such as mercury contained in a vessel 130 enclosing the device. The pipes 3 and 4 communicate at the upper ends, respectively, with the cylindrical chambers 3a and 4a formed in heads 73, 74, and communicate with small nozzles 6 and 7 arranged in the outer walls of the heads 73, 74 respectively, through which the mercury sucked in through the opening 5a emerges as ne jets. Stationary arcuate electrodes or contact segments 8, 8', S, 9, 9', and 9 are arranged so as to occupy the greater part of a circle as shown in Fig. 2, adjoining contact segments being separated by gaps such as 98', 99, 99', 89', SS and S8". Each of the contact segments 8, 3', 8, 9, 9 and 9 Shown in Fig. 2 has a cross-section consisting of a square part (see Fig. 2) provided with an extension such as 72 which is arranged at a small distance 23 from the rotating head 74 of the centrifuge 2.

As -is more clearly illustrated in Fig. la, each of the stationary contacts 8, 8', 8, 9, 9 and 9 illustrated in Fig. 2 have associated therewith feed through 'connectors 231 to 236 which extend externally of the vessel in a vacuum-tight manner. The feed through connectors supply the same potential to opposite fixed contact pairs. The windings 271, 272, 273 represent three phase secondary windings suitably connected by means of leads 241 to 246 to the feed through connectors 231 to 236. One end of each secondary winding is connected to an opposite pair of fixed contacts and the other end is connected by means of the connecting lead 181 to the load 136 and the other end of the load being connected 'by means of the lead 136 to the vessel i3d.

The operation of this device is as follows:

When the centrifuge 2 rotates, mercury is sucked in at the opening 5a and conveyed by the pipes 3, 4 upwards. The mercury passes through the chambers 3a and 4a and is sprayed as a tine jet by the nozzles 6 and 7 against the stationary contacts. The emerging jet of mercury is flattened or squeezed by the short distance 23 at which the heads 73, 74 are arranged from the stationary contacts such as S and 9, reducing thereby considerably the contact resistance theerof with the stationary contacts such as 9. In Fig. 2 the path of thermercury is shown by the 'arrows B. Between the contact segments 3 and 9 and the heads 73, 7d of the centrifuge 2 the mercury trails behind the nozzles 6 and 7 in form of a curtain and drops eventually by its own weight into the mercury pool 5.

In order to accelerate this process the stationary and rotating electrodes can be shaped as shown in Fig. 3 in which the stationary electrodes 308 are curved at the side 362 opposite to the nozzles 3%, the head 310 of the centrifuge 2 being "correspondingly curved at 304. In this Way it `is accomplished that the mercury is gradually deected toward the outside.

When the mercury jet leaves a stationary electrode or contact segment and is Igoing to make contact with the next stationary electrode or contact either an interruption of the current or an overlapping of the contact segment with the following segment, which is Well defined as to time, is desirable according to the use to be made of the device. If the device operates as an inverter, interruption of the current has to be achieved when the jet passes from one segment to the next one, and the next electrode 8 has to be tapered as shown in Fig. 2 at tio in order to allow the mercury curtain to pass Without touching the segment 3. This passing of the curtain is indicated by the arrow B.

The width of the heads 73, 7d of the centrifuge 2 is denoted by l@ in Fig. 2 and should be determined with a View to the maximal overlapping. T he nozzles 6 and 7 are arranged in the heads 73, so as to be shifted as far as possible in the direction of rotation so that the mercury curtain between the stationary electrodes d and 9 and the heads '73, 7d of the centrifuge 2 fills only the width iti. Under circumstances a plurality of nozzles 5 and 7 are required for accomplishing this effect.

Referring now to Fig. 4 the stationary contact segments 498 and dit@ are provided with plane surfaces such as 492, e

4133 which are preferably inclined against the horizontal, the angle of inclination amounting preferably to 45. The heads such as 41d, dil of the centrifuge 2 are provided with corresponding plane faces such as 4M, 495

which are arranged at a short distance from the plane faces such as 492, d3 of the stationary contact segments du@ and iw respectively. The nozzles SiS- and 467 open at right angles to the faces ddd, 465 respectively. Owing to the short distance between the faces db2, 1903 and 404i, @IBS respectively, the mercury forced through the nozzles ditta, 4%7 is squeezed so as to form a curtain-like surface, thereby considerably reducing the contact resistance of the iine jet with the stationary contacts 5:78, di?? respectively, The mercury curtain leaves immediately the faces such as 4432, $93 of the stationary Contact segments d68 and 4569 under the action of the centrifugal force. The mercury curtain strikes then against the inner wall (not shown) of the vessel which Ycan consist of insulating material or of metal provided with an insulation on the inner surface thereof so that the mercury curtain is broken up into droplets. By the inclination of the faces such as 492, 403 the danger of the formation of erratic shortcircuits is minimized. A similar effect is obtained by the embodiment shown in Fig. 3. The mercury droplets co1- lect eventually in the mercury pool 5.

In the embodiment shown in Fig. 5 the slots 122, 123, between the heads Sie, Sii of the mercury centrifuge 2 and the stationary electrode 5%, 509 respectively, are horizontally arranged, the nozzles 596, 597 connected to the cylindrical chambers 3a, Lia respectively opening into the horizontal slots 122, 1.23 at an inclination to the vertical. Thus a mercury curtain 12S, 129 is generated Within the slots 122, 123 which is deflected by an insulating body Tri, i2 or a metallic body which is insulated. The body El, as well as i2, has a curved face 114 opcosita exit of the slot 122 so that the mercury curtain t28 is deflected as shown by the dotted line. The nozzles Sd, 597 are arranged at an inclination against the horizontal and Vertical which imparts to the mercury a direction allowing the jet to pass in the gaps between the stationary electrodes and to be returned in a curve to the mercury pool (not shown) by a suitable formation of the insulating body 11.

The centrifuge body 2 shown in Figs. l and 2 is not a complete solid of revolution in order to save material, but is iiattened at the sides let) and 132 thereof as shown in Fig. 2. ln consequence thereof the sides 14@ and 142 have the tendency to throw the mercury 5 outward so that no mercury would be sucked in through the aperture 5a and the pipes 3, 4- would be empty. In order to prevent this from happening preferably a conical member 14d is arranged coaxially to the centrifuge body 2 and surrounding the opening 5a. The conical member 144 prevents the mercury from being thrown outward.

In the operation of the converting device as a rectier and as an inverter the device is provided with a synchronous motor which changes occasionally the phase position thereof which allows to obtain a commutation without sparks. In order to obtain this phase shift the stator of the driving motor can be rotated in relation to the stationary electrodes. However, this requires, if no elec- 'trical adjusting devices are provided, the gas-tight mounting of a shaft. Since the latter is very diihcult to obtain and provides little safety of operation it is preferable to provide the necessary adjustment by means of a phase shifter arranged outside the rectifier or inverter. Since it is frequently only a question of a few angular degrees which are to be adjusted at increasing loads this can be effected in the most inexpensive manner by means of voltage dividers fed by small transformers. An embodiment of this connection is shown in Fig. 6 in which U, V, W denote the three phases of a three phase mains.

In Fig. 6 three single phase transformers are shown with their primaries 621 to 623 respectively connected across the phases V and W, U and W and U and V. Three voltage divider networks 6M to are connected to the secondary windings 624 to 626 of the transformers, respectively. By shifting the setting of the variable arms 631 to 633 of the voltageV divider networks Gli to 613 respectively7 the phase of the voltages fed to the motor 135 is changed. The phase shifted voltages are connected to the motor 135 by means of connecting leads 633 to 63S.

The mercury centrifuge as described hereinabove is suitable only for center tap connections as they are known from mercury vapor rectifier techniques, because by means of the mercury all metal parts of the casing except the stationary electrodes are imparted a common direct potential. Thus in order to more economically utilize the transformer a bridge connection should be employed which preferably uses two mercury centrifuges, which form respectively, the direct current terminals as shown in Fig. 7 in which the star-connected secondaries 7bit, 702, 703 are connected, respectiveiy, by connections 794-799 each With'one stationary contact by means of feed through connectors 731-736 and 75l-756 of the two mercury centrifuges 710 and 711, respectively. The mercury pool of the centrifuge 711D is connected to the positive terminal 712 of the D. C. line 750 whereas the mercury pool of the centrifuge 711 is connected to the negative terminal 7 i3 of the line,

Current fiow through' thebridge rectifier arrangement will be as follows: Assuming a mercury j'et is bridging contacts 731 and 734 of vesself710,and further assuming that the mercury jet is bridging contacts 752 and 755 of the lsecond vessel 711, then, starting at connection 704 current will ow through feed-throughs 731 and 734, through the mercury pool 5 in the vessel 710Y to the positive terminal of the load 750, through the negative terminal of the load, to feed-throughs 755 and 752, through winding 703,y through winding 701, and back to the feed-throughs 734 and 731. Therefore, 'during the positive half-cycle feed-through contacts 731 to 736 constitute a three-phase commutating rectifying group, and during the negative half-cycle feed-throughs 751 to 756 constitute a second three-phase commutating group. It is of course apparent that this arrangement can also be used as an inverter.

In starting a non-polarized synchronized motor the direction of the voltage is dependent on the moment when the device is switched on. With a center tap connection and a mercury centrifuge advantageously a locking device can be employed which allows the device to operate only at the correct polarity. However, with two synchronous motors and the just described bridge connection the frequent switching on of the two motors independently of each other would consume too much time. On account of this preferably the rotors are excited with direct current having a definite polarity and supplied for instance by a dry rectifier so that the synchronous motors have the right polarity instantaneously at the switching on. In feeding the direct current to each rotor advantageously one slip ring per rotor is used, the other terrninaly of the exciting winding of the rotor being connected to the motor shaft which is connected to the direct current source over the mercury pool.

If the device has to switch larger currents, measures should be taken for increasing the resistance of commutation. In order, however, to dispense with the main chokes or to provide chokes of an inferior quality the mercury jet should be squeezed into curtain shape only during the contact time. During the commutation time the mercury jet should have its normal shape so that the commutation resistance is considerably increased.

As described hereinabove the contacts have contact surfaces formed for instance, like a plane commutator and which are arranged so that the mercury jet or jets make contact with the commutator from below and that the electrodes of the centrifuge body move at such a dis tance that the mercury jet is squeezed into curtain shape during thel main contact time with the electrodes. However, near the gaps between the stationary contacts the distance thereof from the rotating electrode is increased so that the mercury jet is not or only partly squeezed into c urtain shape. Therefore the resistance is increased not only in the ratio of the reduced cross-sectional area but also by the increased length of the mercury jet.

In order to obtain an overlap when the mercury jet changes from one stationary electrode to the other as a rule two or more mercury jets have to be used since one mercury jet forms a satisfactory overlap only if gaps between the stationary contacts are very small which, however, renders it imperative that the voltage between adjacent stationary contacts is very small. The mercury jets are arranged as described hereinabove so as to lead in the direction of rotation so that the trailing mercury curtain completely covers the face of the rotating contact.

Fig. 8 is similar to and operates in a manner similar to the description given for Fig. 5.

` Referring now to Fig. 8a,y 13 denotes the width of the gap between two consecutive stationary contacts 158 and 158. 152 indicates a head of the centrifuge body 2 which is supposed to move in the direction of the arrow The head 152 has a cylindrical chamber 3a from which two nozzles 156 and 155 allow the mercury 6 to escape in form of jets 15 andA 14, respectively. At a position of the head 152 prior to that shown in Fig. 8a the jets 14 and 15 have bridged the stationary contacts 158 and 158' whereas in the position shown in Fig. 8a the jet 15 is in contact with the stationary contact 158' andthe jet 14 extends into the gap 13 and is no longer in contact with the stationary contact 158. The stationary contacts 158 and 158 are provided, respectively, with inclined surfaces 160 and 160. In consequence thereof, in the position shown in Fig. 8a the distance 17 of themouth of the nozzle 156 from the inclined surface 160' is relatively large in comparison to the final distance 122 between the stationary contact 158' and the rotating head 152. Therefore it will be understood that at rst the mercury jets 14 and 15 are not squeezed into curtain shape; however, the jets 14 and 15 are squeezed into curtain shape when the head 152 has moved so far that the mouths of both nozzles 156 and 155 are at the distance 122 from the stationary contact 158'. It is evident that the same applies vice versa if the head 152 leaves the stationary contact 158 and the inclined surface 160 thereof. In this manner it is accomplished that during the commutation time the resistance of the jets is relatively large and is reduced during the contact time. Frequently it is sucient to taper only one of the stationary contacts either at the trailing or the leading end thereof.

By this construction and arrangement of the contacts very considerable advantages are obtained over the devices hitherto known in the art.

First, considerable currents amounting to 1,000 amperes and more can be commutated without sparks between no-load and full-load without having changed anything in the synchronous position of the driving motor.

Second, this arrangement allows to dispense with chokes up to commutation voltages of approximately 50 volts. If the voltage is higher it is advisable to use chokes, if desired, also for controlling the voltage or the current. However, these chokes can be manufactured more inexpensively than the chokes to be provided in contact rectiers having solid contacts which are lifted from the stationary contacts. Thus the no-load voltage is increased without providing further means if the commutation voltage remains below definite limits. If two centrifuges are used in bridge connection as shown in Fig. 7, one centrifuge forming the plus terminal and the other the minus terminal, the arrangement yields a no-load voltage of about 30 volts at a commutating voltage of V22 volts. At the same commutating voltage Uk=22 volts with secondary hexagonal connection according to Fig. 9 in which the stationary contacts of each centrifuge have to be doubled as compared with the three-phase bridge connection, a noload direct voltage of approximately 60 volts is obtained. The phase voltage is denoted in this diagram by Uph. AV further increase is possible by further doubling the number of stationary contact segments to at least twelve for each centrifuge which can be obtained by tapping the hexagonal connection as shown in Fig. l0. In this way a direct voltage of approximately volts is obtained.

This increase of the direct voltage without chokes by further subdivision is rendered possible because the number of the contact segments of the mercury turbine can be considerably increased without increasing the bulk of the turbine whereas in contact rectifiers having lifting bridge contacts the bulk of the device has to be increased for the same purpose. In order to maintain the phase voltages in all cases the hexagonal winding is advantageously supplemented by auto-transformers so that the voltages of the stationary contacts are situated on a circle the radius of which corresponds to the phase voltage Uph as shown in Fig. 11.

Under certain circumstances two mercury turbines can be used. for each direct current terminal, even in bridge connection, the voltages applied to corresponding sta1 tionary contacts of the mercury turbines being shifted against one another by a quantity Uk corresponding to the contact voltage in order for instance to reduce the content in harmonics of the currents in the three-phase mains and to smoothen the ripples of the currents inthe direct current line. The examples given hereinabove form only a selection of the large number of possible solutions of the problem.

In order to control the voltage, preferably chokes are used. For the purposes of the invention, for instance, the main adjustment in coarse stages can he carried out by means of a tapped transformer whereas the tine adjustment is carried out by means of chokes which for instance delay the starting of the device by means of preexcitation, or by delaying the moment of switching. Since the mercury jet rectier is less sensitive than the pressure contact rectiiiers with respect to formation of sparks, chokes having an inferior quality, for instance with cores of silicon can be used.

In order to control the contact time and the voltage, devices are provided which are advantageously used at a high commutating resistance. The chokes provided for large amperages have no longer to accomplish the essential task in the adjustment of the control. For instance besides the stationary contacts movable and adjustable contacts or electrodes can be provided allowing to increase or reduce the contact time according to demand.

Fig. i2 shows diagrammatically a device of this kind in which 8, 8', 8 and 9, 9 and 9 are the stationary contacts or electrodes which areseen from below and contacted by the mercury jets as Vshown in Figs. 2 or 5. The body of the centrifuge is not shown in Fig. l2, however, the plus terminal formed by the mercury pool thereof is shown at i7tl. The stationary electrodes 8, etc., are surrounded by a movable insulating ring member Si on which auxiliary contacts or electrodes 29, 2l and 22 are mounted which serve for changing the contact time.

For instance, the auxiliary contact 2t) is connected by flexible cables 172 and 24S to the stationary contacts 8 and 9, respectively. As the insulating ring SI. is turned in direction of the arrow E the mercury curtain owing olf the stationary Contact 8' hits the auxiliary contact 26 and thus connects the stationary contacts 8 and 8 so that the contact time is increased. lf, however, the insulating ring l is turned back in a direction opposite to the arrow E the contact timeis reduced to the minimum of overlapping.

The device operates with mercury jets in opposite drections and is intended for 1500 revolutions per. minute at 50 cycles per second. Thus always two main contacts, for instance 8 and 3 are provided.

In contradistincition to Contact rectifiers with solid contacts, the increase of the number of the contact segments offers no difficulties. Therefore chokes can be connected in series with the auxiliary contact, such chokes being shown in Fig. l2 for the auxiliary contacts 2t), 2l, 22 and denoted by 515, 524 and 536, respectively. The chokes 515, 524 and 536 carry currents only during the commutation time or a part thereof while the commutation is essentially carried out at an increased resistance of the mercury jet. Therefore the main losses caused by the use of chokes are avoided. At least it is possible, if main chokes indicated by 54, 55 and 56 and auxiliary chokes such as 515, 524 and 536 areY used, to design the main chokes for a much lesser amperage so that they are cheaper than chokes of a Contact rectifier having solid contacts. In the example the current flows when the stationary contacts 3" and 9 are operated 'to the plus terminal of the device as indicated by the arrows forming part of the dotted lines, the mercury jets owing in reverse direction. If the mercury jets are in touch with the contacts S, 9 and the auxiliary contact 21, the current over the electrode 8" fades out over the choke 524 and the auxiliary Contact 21. Since the choke 524 has flowing there Vthrough a portion of the rectified current only during a very short time, it can be equipped for the optimal minimum current without regard for the losses. Since also inductive voltage losses have not to be taken into consideration during the main switching time, ordi nary silicon iron can be used for the chokes, and not even ring cores are required but the ordinary box-like cores (geschachtelte Kerne).

if desired, the auxiliary contact 20 can be so arranged that no flexible connection to the main contact is required, the connection being formed by the mercury jet or curtain der'iected backwards.

Fig. 13 illustrates another embodiment of the present invention consisting of a trailing adjustment of the rotating mercury centrifuge; the thus increased currents of the precedingV or succeeding phase are again rendered ineffective by the increased commutation resistance of the mercury jet. The adjustment should be effected by either adjusting the flange of the motor il for instance by means of a gear including toothed wheels 301, the driving shaft of which is led in vacuum-tight manner outside the casing 137. Or the adjustment can be carried out electrically by means of a driving motor 363 either within or outside the gas-tight casing. Manual adjustment is also possible.

The phase lag can be obtained by purely electrical means, for instance, by rotating the pbase position of the three-phase voltage of the driving motor.

Fig. 14 illustrates a further possibility for adjusting phase lag which consists in providing the armature with direct current windings which are electrically displaced about either one or the other winding being fed with more or less direct current so that the armature can be correspondingly adjusted in this range. Preferably the exciting windings bt, 851 and 352, 852 are connected at one end thereof to the shaft 7 of the armature 85% whereas the other ends thereof are connected to slip rings 853, 854, respectively, provided for this purpose. The transfer of direct current to the shaft of the armature is effected by the mercury. At the same time, if an auxiliary source of direct current such as 996' is provided, a synchronizing of the mercury turbine with correct polarity is obtained. A further embodiment of the present invention consists in arranging two mercury centrifuges in bridge connection, the rotors being rotated out of the synchronous position in order to adjust the contact time as described hereinabove. This also can be provided without special means.

At larger powers it has been found to be necessary to observe the interior of the mercury turbine in order to ascertain whether a damaging sparking occurs. In order to accomplish this preferably iron vessels are provided with a vacuum-tight window which has to be resistant to heat (see Fig. 7; 72b, 722i). The enclosing vessel can be either permanently under the pressure of, for instance, a communal gas pipe or of bombs containing a protective gas, preferably pressures exceeding the atmospheric pressure being used in order to obtain a good extinction of the sparks and arcs. Under circumstances a special high vacuum pump can be provided if the packings of the device cannot be maintained gas-tight over longer periods of time.

if a bridge connection is used, at least two centrifuge casings are provided having each a driving motor because otherwise the two mercury casings can be electrically insulated from each other only with difficulty. If, however, a plurality of gas-tight centrifuge shafts is provided, a common driving motor can be aranged outside the turbines, the driving members of which have to be insulated. This construction is possible without reducing the protective gas atmosphere after a longer period of operation, particularly if the vessels are maintained under pressure from the outside or if desired, are maintained under vacuum. lf the two turbines and the motor are enclosed in the gas-tight vessel the insulation offers difficulties because mercury escaping along the shaft of the 9 turbines may cause short-circuits. In this case s'ic'ient space for collecting the mercury even over longer periods of operation and suflicient quantities of mercury 1n the two turbine vessels have to be provided.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of contact rectifylng devices differing from the types described above.

While the linvention has been illustrated land described as embodied in a contact rectifying device having a rotating mercury jet, it is not intended to be limited to the details shown, since Various modifications and structural changes may be made without departing in any Way from the spirit of theA present invention.

Without further analysis, the foregoing will so fully reveal the gist of the -present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, yfairly constitute essential characteristics of -the generic or specific aspects of this invention and, therefore,` such adaptations should and are intended to `be comprehended within the meaning and range of equivalence of the `following claims.

What is claimed as new and desired to 'be secured by `Letters Patent is:

1. In a converting device, in combination, a plurality of stationary contacts arranged along a circle and separated from one another `by gaps; a rotating contact including means for directing a rotating electro-conductive jet stream against said stationary contacts in succession, said jet stream forming a continuous electrically-conductive path between said rotary contact and each of -said stationary contacts respectively in succession; and means for imparting a curtain-like shape to said jet stream so as to `decrease the resistance of said electrically-conductive path, said curtain-shaped jet stream being forced by centrifugal force into said gaps between said stationary contacts.

2. In a converting device, in combination, a plurality lof stationary contacts 'arranged along a circle and separated 'from one another by gaps; a hollow rotating contact, said rotating contact rotating on a circle concentric with, and having a diameter being slightly smaller than the diameter of, said circle along which said stationary contacts are arranged; and means for forcing an electro-conductive liquid through said rotating contact, said liquid forming a jet stream being squeezed into a curtain-like shape when said rotating contact passes along each of said stationary contacts to forrn a continuous electrically-conductive path between said rotating contact and the respective stationary contact, said curtainlike jet being forced by centrifugal force into said gaps between said stationary contacts.

Y3. A converting device, comprising, in combination, a closed vessel; a plurality of stationary contacts arranged in said closed vessel along a circle and separated from one another by gaps, said stationary contacts having stationary contact faces; a hollow body arranged for rotation in said closed vessel, said hollow body having a rotating contact face rotating on a circle concentric with, and having a diameter being slightly smaller than the diameter of, said circle along which said stationary contacts are arranged, said rotating contact face having substantially the same shape as said stationary contact faces, said hollow body having an opening arranged at the lower end thereof and a nozzle opening in said rotating contact face;` and a pool of mercury arranged in said closed vessel so as to cover said opening arranged at said lower end of said hollow body, whereby by the rotation of said hollow body mercury is sucked in through said opening and forced out of said hollow body through said nozzle as a jet stream which is squeezed into curtain-like shape when said rotating contact face passes along each of said stationary contacts, said curtain-like shaped jet stream forming a continuous electrically-con- Ycontact face rotating on a p ,having a diameter being slightly smaller than the diameductive path between said rotating contact face and the respective stationary contact face, said curtain-like jet `stream being forced by centrifugal force into said gaps between said stationary contacts andl being thrown against the walls of said vessel Where said jet stream 1s broken up into droplets collecting in sald pool of mercury.

4. In a converting device as claimed in claim 3, wherein said hollow body has an axis of rotation, said stationary contact faces and said rotating contact face being ,parallel to said laxis of rotation and said gaps separating zsaid stationary contacts from one another being formed so that said curtain-shaped jet stream extends Vtangentially to said circle of rotation of said rotating 'contact face to make electrical contact with the next successive stationary contact for a desired duration.

5. In a converting `device as claimed in claim 3, wherein said stationary and rotating contact faces are inclined tothe axisof rotation of said hollow body.

6. In a converting device as claimed in claim 3, wherein ksaid contact faces .are Curved to deflect the curtainshaped jet stream of mercury toward the bottom of said closed vessel.

7. In aconverting device as claimed in claim 3, wherein said hollow body has an axis of rotation forming right angles with said contact faces, said nozzle being arranged Vso that said mercury jet stream avoids said gaps separating said stationary contacts from one another; and an insulated guiding body arranged outside said stationary contacts and guiding the curtain-shaped mercury jet vstream back into said pool arranged in said closed ves- Vclosed vessel along a circle and separated from one another by gaps, said stationary contacts having stationary contact faces; a vhollow body arranged for rotation in said .closed vessel, said hollow body having a rotating circle concentric with, and

terof said circle along which said stationary contacts are arranged, said rotating contact face having substantially the same shape as said stationary contact faces, said hollow body having an opening arranged at the lower end thereof and a plurality of nozzles opening in said rotating contact face; and a pool of mercury arranged in said closed vessel so as to cover said opening arranged at said lower end of said hollow body, whereby by the rotation of said hollow body mercury is sucked in through said opening and forced out of said hollow body through said nozzles as jet streams which are squeezed into curtainlike shape when said vrotating contact face passes along each of 'said stationary contacts, said curtain-like jet streams lling substantially the entire volume between the rotating contact face and the respective Stationary contact face to form a continuous electrically-conductive path therebetween, said jet streams being forced by centrifugal force into said gaps between said stationary contacts andbeing thrown against the walls of said vessel where said jet is broken up into droplets collecting in said pool of mercury.

l0. A converting device as claimed in claim 3, having a synchronous motor for driving said hollow body; and a plurality of transformers connected in circuit with the stator winding of said motor for adjusting the phase position of said synchronous motor.

ll. A Contact converter, comprising, in combination, two converting devices as claimed in claim 3; and a bridge connection including said converting devices, one of said converting devices forming the positive D. 'C. terminal Awith said stationary contacts so that the contact ,time

between said rotatable contacts and said stationary contacts can be changed.

13. A converting device as claimed in claim 3, having at least one choke connected in circuit with said stationary contacts.

14. A converting device as claimed in claim 3, having a synchronous motor for driving said hollow body, wherein the phase position of the synchronous motor is adjusted with a direct current excitation; and at least two direct current excited windings being shifted with respect to each other by 90 and being differently excited according to the desired phase position, said windings having a common terminal connected by means of the armature shaft to said mercury pool, the other terminals of the exciting windings being energized by means of slip rings.

l5. A converting device as claimed in claim 3, including means for maintaining the interior of the closed vessel under positive pressure of a protective gas.

16. A converting device, comprising, in combination, a closed vessel; a plurality of stationary contacts arranged in said closed vessel along a circle and separated from one another by gaps, said stationary contacts having stationary contact faces; a hollow body arranged for rotation in said closed vessel, said hollow body having a rotating contact face rotating on a circle concentric with,

,and having a diameter being slightly smaller than the vdiameter of said circle along which said stationary contacts are arranged, said rotating contact face having substantially the same shape as said stationary contact faces, said hollow body having an opening arranged at the lower end thereof and a nozzle opening in said rotating contact face; a pool of mercury arranged in said closed vessel so as to cover said opening arranged at said lower end of said hollow body, whereby by the rotation of said hollow body mercury is sucked in through said opening and forced out of said hollow body through said nozzle as a jet stream which is squeezed into curtainlike jet stream when said rotating Contact face passes along any of said stationary contacts, said curtain-like jet stream being forced by centrifugal force into said gaps between said stationary contacts and being thrown against the wall of said vessel where said jet stream is broken up into droplets collecting in said pool of mercury; a synchronous motor for driving said hollow body; and means for changing the phase position of said synchronous motor.

17. A converting device, comprising, in combination,

a closed vessel; a plurality of stationary contacts ar-V ranged in said closed vessel along a circle and separated from one another by gaps, said stationary contacts having stationary contact faces; a hollow body arranged for rotation in said closed vessel, said hollow body having a rotating contact face rotating on a circle concentric with, and having a diameter being slightly smaller than the diameter of said circle along which said stationary contacts are arranged, said rotating contact face having substantially the same shape as said stationary contact faces, said hollow body having an opening arranged at the lower end thereof and a nozzle opening in said rotating contact face; a pool of mercury arranged in said closed vessel so as to cover said opening arranged at said lower end of said hollow body, whereby by the rotation .of said hollow body mercury is sucked in through said opening and forced out of said hollow body through said nozzle as a jet stream which is squeezed into curtain-like jet stream when said rotating contact face passes along any of said stationary contacts, said curtain-like jet stream being forced by centrifugal force into said gaps between said stationary contacts and being thrown against the wall of said vessel where said jet stream is broken up into drop- Ylets collecting in said pool of mercury; a synchronous motor for driving said hollow body; and gear coupling Ymeans operatively connected to the stator of said syn- Vchronous motor for `changing the phase position of said synchronous motor.

- 18. A converting device, comprising, in combination, a closed vessel; a plurality of stationary contacts arranged in said closed vessel along a circle and separated from one another by gaps, said stationary contacts having stationary contact faces; a hollow body arranged for rotation in said closed vessel, said hollow body having a rotating contact face rotating on a circle concentric with, and having a diameter being slightly smaller than the diameter of said circle along which said stationary contacts lare arranged, said rotating contact face having substantially the same shape as Vsaid stationary contact faces, said hollow body having an opening arranged at the lower end thereof and a nozzle opening in said rotating Contact face; a pool of mercury arranged in said closed vessel so as to cover said opening arranged at said lower end of said hollow body, whereby by the rotation of said hollow body mercury is sucked in through said opening and forced out of said hollow body through said nozzle as a jet stream which is squeezed into curtain-like jet Vstream when said rotating contact face passes along any of said stationary contacts, said curtain-like jet stream being forced by centrifugal force into said gaps between said stationary contacts and being thrown against the wall of said vessel where said jet stream is broken up into droplets collecting in said pool of mercury; a syn- Achronous motor for driving said hollow body; and manually operated gear coupling means operatively connected to the stator of said synchronous motor for changing the phase position of said synchronous motor.

References Cited in the le of this patent UNITED STATES PATENTS 690,973 Luschka Jan. 14, 1902 788,279 Porter et al. Apr. 25, 1905 1,136,058 Sperry Apr. 20, 1915 1,251,126 Snook Dec. 25, 1917 1,577,685 Bradley Mar. 23, 1926 2,351,975 Koppelmann .lune 20, 1944 2,438,067 Luhn Mar. 16, 1948 f 2,444,687 Widakowich July 6, 1948 2,583,263 Goldstein Jan. 22, 1952 2,609,461 Holcomb et al. Sept. 2, 1952 2,617,975 Aeschlimann Nov. 11, 1952 FOREIGN PATENTS 130,537 Great Britain Aug. 7, 1919 V174,523 Great Britain Feb. 2, 1922 191,701 Great Britain Aug. 16, 1923 192,704-A Great Britain May 1, 1924 

